1. Field of the Invention
The present invention relates to laser endovascular treatments and in particular, to the treatment of vascular pathologies, such as venous insufficiency, with laser energy using an optical fiber set and low power densities.
2. Invention Disclosure Statement
The human venous system of the lower limbs consists essentially of the superficial venous system and the deep venous system, both connected by perforating veins. The superficial system comprises the great and the small saphenous veins, while the deep venous system includes the anterior and posterior tibial veins, which converge to form the popliteal vein near the knee. The popliteal vein, in turn, becomes the femoral vein when joined by the small saphenous vein.
The venous system comprises valves, whose main function is to achieve unidirectional blood flow back to the heart. Venous valves are usually bicuspid valves, with each cusp forming a blood reservoir, which force their free surfaces together under retrograde blood pressure. As a consequence, when properly operating, retrograde blood flow is prevented, allowing only antegrade flow to the heart. A valve becomes incompetent when their cusps are unable to seal properly under retrograde pressure gradient, so retrograde blood flow occurs. When retrograde blood flow occurs, pressure increases in the lower venous sections, dilating veins and usually leading to additional valvular failure.
Valvular failure, usually referred to as venous insufficiency, is a chronic disease that can lead to skin discoloration, varicose veins, pain, swelling and ulcerations. Varicose veins refer to blood vessels that have become enlarged and twisted and have progressively lost their wall elasticity. Owing to the widening of the blood vessels, vein valves cannot be completely closed and veins lose their ability to carry blood back to the heart. This leads to an accumulation of blood inside the vessels, enlarging and twisting the veins even more. Furthermore, varicose veins usually have a blue or purple color and may protrude twisted above the surface of the skin, being responsible of their characteristically unattractive appearance. They are commonly formed in the superficial veins of the legs, which are subject to high pressure when standing. Other types of varicose veins include venous lakes, reticular veins and telangiectasias.
There is a number of treatments available intending to eradicate these kinds of vascular pathologies. Some of them only consist in relief of symptoms because they do not prevent new varicose veins from forming. These include elevating the legs by lying down or using a footstool when sitting, elastic stockings and exercise.
Varicose veins are frequently treated by eliminating the insufficient veins. This forces the blood to flow through the remaining healthy veins. Various methods can be used to eliminate the problem insufficient veins, including sclerotherapy, surgery, electro-cautery, and laser treatments.
Sclerotherapy uses a fine needle to inject a solution directly into the vein. This solution irritates the lining of the vein, causing it to swell and the blood to clot. The vein turns into scar tissue that fades from view. Some physicians treat both varicose and spider veins with sclerotherapy. The sclerosant acts upon the inner lining of the vein walls causing them to occlude and block blood flow. This method has numerous complications. People with allergies may suffer allergic reactions, occasionally severe. The sclerosant may burn the skin, if the needle is not properly inserted or permanently mark or stain the skin. Furthermore, sclerotherapy can lead occasionally to blood clots. Moreover, treatment is limited to veins of a particular size and range as larger varicose veins may be more likely, according to many studies, to recur if treated with sclerotherapy.
Surgery to treat varicose veins, commonly referred to as “stripping,” is usually done under local or partial anesthesia. Here, the problematic veins are stripped out by passing a flexible device through the vein and removing it through an incision near the groin. Smaller tributaries of these veins also are stripped with this device or removed through a series of small incisions. Those veins that connect to the deeper veins are then tied off. Surgery also results in scarring where small incisions are made and may occasionally cause blood clots. Furthermore, procedures are long and require long recovery periods.
These surgical therapies show several disadvantages compared to other approaches. One of them is the need of general, loco-regional or peridural anesthesia. Furthermore, these procedures may damage collateral branches of the vein which may consequently bleed, giving rise to hematomas, or may lead to other complications such as blood loss, pain, infection, nerve injury and swelling. Moreover, because of the damage done to the treated area, patients may have pain and discomfort for hours and even days after surgery. Side effects of this method of removing varicose veins are those for any surgery performed under anesthesia, including nausea, vomiting, and the risk of wound infection.
Another well known method of treating insufficient veins is through the use of radio frequency (RF). An example of the application of this method can be found in U.S. Patent Publication No. 2006/0069471, by Farley et al. Electrodes are introduced through a catheter inside the vein to be treated for insufficiency and RF is applied to cause selective heating of the vein. The catheter is positioned within the vein to be treated and the electrodes on the catheter are moved toward one side of the vein. RF energy is applied in a directional manner from electrodes at the working end of a catheter to cause localized heating and corresponding shrinkage of the adjacent venous tissue. This method has some disadvantages. The use of RF energy in the treatment of vein insufficiency may be ineffective in certain cases and interventions can be lengthy and stressful for the patient. Nevertheless, it is still a popular local energy treatment among physicians. There are minimally invasive surgical options for the treatment of blood vessels. The alternatives preferred by those skilled in the art are those that use laser radiation. Laser surgery has been improved due to new diode laser systems. For endovascular laser surgery, laser radiation applies thermal energy to the vein with the aid of an optical fiber, and while it is withdrawn the vein closes and eventually disappears through absorption. In these and other cases, endovascular laser treatment provides an effective technique for eliminating to skin and vascular problems. Moreover, it still provides a closer access to the treatment area, allowing less powerful laser equipments and less skin or healthy tissue damage. This in turn reduces costs while at the same time provides a shorter recovery period due to less damage of skin and surrounding healthy tissue.
In most cases, endovascular laser treatment can be summarized as follows: first of all, a guide wire is inserted into the vein to be treated, preferably with the help of an entry needle. Secondly, an introducer sheath and catheter are inserted together over the guide wire. Then the introducer sheath combination is advanced to a desired position. When it is properly positioned, the guide wire first and then the introducer sheath are removed leaving the catheter in place. Subsequently, the optical laser fiber (coupled to a laser source) is inserted into the catheter and positioned so the fiber's distal tip and the catheter are at the same point. After that, anesthesia is applied. Usually tumescent anesthesia is applied to the vein to be treated for isolating the vein from perivenous tissue and diminishing vein diameter. Previous to lasing, the catheter is pulled back so that the distal end of the fiber is exposed near the treatment area of the vein. Finally, the laser source is activated to irradiate vein interior while slowly withdrawing laser fiber and catheter together, at a rate, e.g., of 2 to 3 mm per second, to treat and close a desired length of the vein.
In U.S. Patent Publication No. 2007/0260229, Navarro et al. disclose a method and kit for endovenous laser treatment in which previous to applying energy, a sclerosing agent is injected into the vein. Sclerosing agent irritates the inner layers of the vein causing it to collapse. This makes posterior lasing more effective. Sclerosing agents do not however, have an analgesia effect and therefore anesthesia must be applied in addition to this, making the procedure more complex and longer lasting. Furthermore, this method has the disadvantages of sclerotherapy mentioned earlier.
Endovascular vein surgery many times requires anesthesia as the patient is not always prepared or willing to support any type of possible discomfort or pain.
Three main anesthetic techniques are commonly used in varicose vein surgery: general anesthesia, central nerve block and tumescent anesthesia.
General anesthesia or central nerve block has many possible adverse effects such as muscle rigidity and airway irritation at induction, hypotension and bradycardia intraoperatively, nausea, vomiting postoperatively. Also, if used in day surgery, the time to discharge can be many hours after surgery.
Some skilled in the art use other techniques such as external application of cold, or topical anesthesia, but these are at times insufficient to provide adequate analgesia. Furthermore, there are other effects desired when carrying out anesthesia for vein treatment. Some tumescent liquids cause vein contraction and this allows for a more uniform and effective irradiation. Other liquids enhance laser radiation absorption properties of vein, again allowing for a more effective vein closure.
Both Tumescent Anesthesia and general anesthesia provide adequate relief from pain, but Tumescent Anesthesia minimizes blood loss, bruising and post procedural discomfort. It is a technique for delivery of large volumes of liquid in a perivascular area.
The word “tumescent” means swollen or firm. A large volume of liquid is delivered subcutaneously into target tissue. Dr. Jeffrey Klein, a dermatologist, first developed Tumescent Anesthesia, in liposuction techniques. He used a diluted solution of a local anesthetic, epinephrine, sodium bicarbonate and normal saline to numb the areas to be treated and to minimize the bruising and bleeding that would otherwise complicate any liposuction procedure. It improved patient safety, the precision of the liposculpture procedure and patient satisfaction and convenience.
In U.S. Patent Publication No. 2006/0253112, Suarez et al. propose, in cosmetic laser treatment device and method for localized lipodystrophies and flaccidity, a saline solution inserted into the treatment site to aid in the heating of fat cells and their eventual destruction as well as their removal. This was an advantage to prior art in that the tumescent solution applied also improved energy absorption of target tissue.
Goldman et al. proposed the use of tumescence in vein treatment with RF. In U.S. Pat. No. 7,396,355 they disclose a method and apparatus for applying energy to a hollow anatomical structure such as a vein, to shrink the structure. The invention is directed to pre-compressing and exsanguinating vein while providing anesthesia by delivering fluid to vein tissue in order to induce tumescence and consequent compression of the hollow anatomical structure during a procedure of applying energy from within the structure. The method described is specific of vein treatment techniques that apply RF energy and, as mentioned earlier, even in the case that the application of the disclosed method of tumescence, technique has proven to be ineffective in comparison to current state of the art. Furthermore, the procedure of exsanguination can be tedious and time consuming and in addition, it is not desired in endovenous laser treatments that apply laser wavelengths such as 980 nm which is highly absorbed by hemoglobin or 1470 nm which is highly absorbed by water, the main component in blood. Doing this would make procedure much less effective.
Tumescent anesthesia has been applied with increasing success in endovascular laser vein treatment. Once optical laser fiber is in place within the vein, before applying laser radiation, a considerable amount of tumescent solution is delivered subcutaneously. A common procedure is to make a number of percutaneous injections of a tumescent anesthetic agent under ultrasonic guidance along the entire length of the affected vein into the perivenous space. An appropriate method using tumescent solution should achieve local analgesia and constriction of the vein compressing the fiber inside it.
There are numerous disadvantages associated with this method of administering local anesthesia injections. It is tedious and time consuming because of the amount of necessary injections. Injections may be painful for the patient and leave puncture wounds. Finally, as pointed out by Holdstock et al. in some cases, the standard technique of tumescent anesthesia by needle injections may cause damage to laser fiber (J. M. Holdstock, P. Marsh, M. S. Whiteley, B. A. Price. It is Possible to Cause Damage to a Laser Fibre during Delivery of Tumescent Anaesthesia for Endovenous Laser Ablation (EVLA), Eur J Vase Endovasc Surg (2008) 36, 473-476).
In U.S. Pat. No. 7,163,533 Hobbs et al. propose a solution to address these problems. They claim a catheter device for treating vascular disease, comprising catheter to be inserted into blood vessel and including lumen(s) through which energy delivery device and fluid are received, and exits disposed in sidewall of catheter. The catheter device includes an energy delivery device such as an optical fiber for delivering laser energy and a catheter. The catheter lumen receives the optical fiber and a fluid such as an anesthetic agent or vasoconstricting agent. According to the invention, a plurality of exits is formed in the sidewall of the catheter. The exits are in communication with the catheter lumen and administer the fluid into the blood vessel, well before the leading treatment area and behind the fiber tip. This device and method are not ideal for effective laser treatment as tumescent liquid is released through the sides of catheter sheath and not up front, where laser fiber tip is and therefore not nearby the place where lasing will immediately take place. It teaches counter to the present invention.
Prior art mentioned above presents a series of possible complications when applying tumescent or other anesthesia in endovascular laser treatment of varicose veins, including temporary discomfort, swelling, bruising, areas of hyperpigmentation, and hematoma.
There is therefore a need for an improved method and device for providing anesthesia in vascular surgery. The improved method and device should eliminate possibility of pain, safely and without discomfort for the patient, while applying energy to a vein. It should also enable more efficient and enhanced treatment of the problem veins. Present invention addresses these needs.